Heterologous expression and site-directed mutagenesis of an ascorbate-reducible cytochrome b561

A. Bérczi, Dan Su, Mahadevan Lakshminarasimhan, Amy Vargas, Han Asard

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Cytochromes b561 (Cyts b561) are ubiquitous membrane proteins catalyzing ascorbate-mediated trans-membrane electron transfer. A heterologous expression system in Saccharomyces cerevisiae was developed to study their structure-function relationship. Recombinant mouse chromaffin granule Cyt b561 (CGCytb) shows spectral characteristics, ascorbate reducibility, and redox potentials identical to that of the native bovine protein. Moreover, the reconstituted recombinant protein mediated trans-membrane electron transport with kinetic characteristics similar to that of bovine CGCytb. Site-directed mutant analysis supports the presence of two hemes coordinated by the highly conserved His pairs H52/H120 and H86/H159. Reduction of CGCytb by ascorbate showed biphasic kinetics (Kd1: 0.016 ± 0.005 mM, K d2: 1.24 ± 0.19 mM). Mutation of a well-conserved Arg residue (R72) abolished high affinity CGCytb reduction by ascorbate, indicating that this residue may be critical for substrate binding. On the other hand, mutation of a Lys previously suggested to play a role in ascorbate binding (K83), did not affect the ascorbate-mediated reduction of the protein.

Original languageEnglish
Pages (from-to)82-92
Number of pages11
JournalArchives of Biochemistry and Biophysics
Volume443
Issue number1-2
DOIs
Publication statusPublished - Nov 15 2005

Fingerprint

Chromaffin Granules
Mutagenesis
Site-Directed Mutagenesis
Membranes
Kinetics
Heme
Recombinant Proteins
Yeast
Mutation
Membrane Proteins
Proteins
Electron Transport
Oxidation-Reduction
Saccharomyces cerevisiae
Electrons
Substrates
cytochrome b561

Keywords

  • Ascorbate
  • Cytochromes b561
  • Electron transport
  • Heterologous expression
  • Membrane proteins
  • Site-directed mutagenesis

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

Cite this

Heterologous expression and site-directed mutagenesis of an ascorbate-reducible cytochrome b561. / Bérczi, A.; Su, Dan; Lakshminarasimhan, Mahadevan; Vargas, Amy; Asard, Han.

In: Archives of Biochemistry and Biophysics, Vol. 443, No. 1-2, 15.11.2005, p. 82-92.

Research output: Contribution to journalArticle

Bérczi, A. ; Su, Dan ; Lakshminarasimhan, Mahadevan ; Vargas, Amy ; Asard, Han. / Heterologous expression and site-directed mutagenesis of an ascorbate-reducible cytochrome b561. In: Archives of Biochemistry and Biophysics. 2005 ; Vol. 443, No. 1-2. pp. 82-92.
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